Maintain Page state if one servlet is calling another servlet

I am working on webbased application using Tomcat, application flow is -
There is one jsp A.jsp from where we select some fields and submit it which calls myServlet.java; MyServlet.java is used to display information inside popup screen using out.println().
My Problem is - popup screen have one link to open pdf file and clicking that link calls PdfServlet.java that opens a pdf file, pdfServlet.java have following header info -

Now problem is creating here --- why back arrow given on browser is refershing A.jsp, i dont' want to reset my info. I just need the page state as it is for which i am creating the pdf. why its reset all info on back; is it because link is opened from popup screen not from A.jsp? how i can get the same state without making any flow change menas print link always be on pop up screen.